Power hacksaw machine



Aug. 4, 1936. A, RAsMUssEN POWER HACKSAW MACHINE Filed Oct. 26, 1934Patented Aug. 4, 1936 sTATss PATENT oFFlcE l 2,049,626' n POWER HAcKsAWMACHINE AndrewA Rasmussen, Racine, Wis. Application ocwber'as, 1934,serial No. 750,063

s claims. (o1. 29-73) This invention relates to improvements in powerhack saw machines, and more particularly to means for controlling thefeeding of the saw blade relative to the work during the cuttingstrokes.

The present improvements are herein shown as applied to the type of hacksaw illustrated in the Rasmussen Patent #1,211,964, wherein thereciprocating saw frame is normally overbalanced in such manner thatwhen the feed mechanism is released, the saw frame will be overbalancedto carry the saw away from the work. This occurs at the end of thecutting stroke whereby the saw does not drag on the bottom of the workduring its non-cutting or return stroke.

Among other things a general object of the invention is to provide anovel hydraulic feed mech-V anisrn Yfor power hack saw machines combinedwith means for gradually building up the feed The prior Rasmussen Patent#1,334,166, sought to accomplish the last-mentioned object by theprovision of pneumatic cushioning means in conjunction with the feedmechanism for gradually building` up the feed pressure and forcushioning the feed of the saw blade.

In said prior construction, however, it was found that it was essentialto initially buildup a predetermined pressure within the pneumaticcushioning chamber, since it was necessary to overcome the force of theoverbalancing spring for the saw frame before the saw could cut into thework. This initial building up of vpressure took quite 'a length of timeand therefore detracted from the efficiency of the machine. In addition,due to the inherent peculiarities of air used in the cushioning chamber,it was found that after the pressure had been built up to overcome theoverbalancing spring, the build up of the pres- 40 sure thereafter couldnot be accurately controlled,

and vthe vpressure would increase too rapidly and Vtoo much force wouldbe applied to the saw frame. f

It is, therefore, a primary object of the present invention to overcomethe afore-mentio-ned difculties attendant tothe incorporation of apneumatic cushioning chamber in a power hack saw hydraulic feedmechanism, by providing, in lieu of a pneumatic cushioning chamber, aconfined spring controlled arrangement, whereby no time is lost at theoutset and the saw will commence cutting at the-first stroke of the pumpwhen the saw is in Contact with work, and in addition,

thereafter as additional pressure is required on the saw frame, thespring will be gradually compressed at a controllable predeterminedrate. By this arrangement the saw will operate at the greatest efciencyand it will not be subjected to undue strain nor be damaged.

A further specific object of the invention is to 5 provide in a powerhack saw machine, spring controlled means for determining the build-upof pressure applied to the saw frame, said spring controlled means beingequipped with an integral indicator to show at all times the amount ofpres- 10 sure actually being applied to the saw or failure of someportion of the apparatus.

A further specific object of the invention is to provide in a power hacksaw machine, manually operated selective means for limiting the maxi- 15mum build-up of pressure attainable.

A further object of the invention is to provide a'power hack saw machinewhich is of simple construction, is strong and durable, is eflicient inits operation, and which is well adapted for the 20 purposes set forth.l

With the above and other objects in View the Vinvention consists of theimproved' power hack saw machine, Vand its parts and combinations as setforth in the claims, and all equivalents there- 25 of. Y

In the accompanying drawing in which the same reference charactersindicate the same parts in all of the views:

Fig. 1 is a side View of a power hack saw to 30 Y which the invention isapplied, showing the feed and pressure build-up mechanisms in verticalsection, portions of the saw mechanism being broken away;

Fig. 2 is an enlarged, fragmentary, detail sec- 35 l tional View of therelief valve control mechanism;

and

Fig. 3 is a sectional View thereof taken on line 3 3 of Fig. 2.

Only those portions of the power hack saw nra- 40 VYmember I4 ispivotally attached, adjacent its rear end, to the main drive shaft I5 ofthe machine. 5 0

-Said frame guide and support carries at its forward'end the usualslide. saw frame I6 between the legs of which is stretched a hack sawblade I1. The weight of the vertical swinging saw frame y guide'and thesaw fratrie carried thereby is coun- 55 1 a closed distributing passage6I.

terbalanced so that the outer end of the supporting frame and guide whennot under the influence of the feeding mechanisms, tends to swing awayfrom the saw table. This overbalancing effect can be produced by eitheroverweighting the swinging saw supporting frame rearwardly of the maindrive shaft I5, or it may be effected by spring pressure. For thepurpose of illustration, the latter means is employed, and it will beseen that arod or link 2D is loosely connected at its upper end'to atail piece 2| of the frame I4. The rod 26 extends through an aperturedportion of the table and below the table and surrounding the rod is acoiled spring 22 which is conned between a shoulder on the table andcertain nuts 23 -threaded onto the lower end portion of the rod. Thenuts 23 may be adjusted on the rod to vary the tension exerted by thespring.

The reciprocating saw frame |6 is operated through the medium of apitm'an 25 which is pivotally connected at one end 21 to the saw frameand at its other end to a crank disc 29 by means of a crank pin 28. Thedisc 29 is secured to and rotates with the main drive shaft I5. Saidshaft is provided with the usual tight and loose pulleys 35 and 3|providing means whereby power may be Y applied to operate the machine.

The feed mechanism for the power hack saw fra-me includes a feedcylinder 35 provided with a lower cylinder head 35 and an upper cylinderhead 31. Within said cylinder there is a piston 38 having a piston rod39 extending through a bearing in the cylinder head 31. The cylinderwall is provided with a guide extension provided with diametricallyoposed guide slots 4I. Attached to and depending from an intermediateportion of the saw frame guide and support |4 is an arm 43 which isadapted to rise and fall with said member i4. The lower end of said arm43 is loosely connected to a link 45 by means of a. pin 44. The link, inturn, is loosely connected at its lower end by a pin 46 with the upperendof said piston rod 39, said connection being above the upper head ofthe cylinder. The piston rod is also provided at `its upper end portionwith oppositely extending guide arms 48 which extend into said guideslots 4I and constitute means for guiding the link 45 and the upper endportion of the piston rod.

A vertical pump cylinder is indicated generally by the numeral 50 and insaid cylinder an elongated plunger I is adapted to reciprocate. Formedintegral with the pump cylinder 5|) is another cylinder 52 adapted tocontain a reciprocal plunger 53.

Ext/ending from the Vlower end ofthe cylinder 50 is an intake 54 throughwhich a fluid, such as oil, is drawn into the cylinder 50 when theplunger 5| rises therein. Said intake passage is controlled at its upperend by a ball valve 55. As illustrated, said ball valve is arranged sothat it is pressed downwardly against an upwardly facing seat in theupper end of the passage 54 by means of a spring 55 suitablyenclosedwithin the lower end of the cylinder 50. The lower end of said cylinder58 is also provided with a discharge port 60 which affords communicationbetween -said cylinder and As will hereinafter appear the feed pressureis built up within said passage 6|. The port 60 is arranged with adownwardly facing seat engaged by a ball valve 62 yieldably held inposition by a suitably mounted and conned spring 63.

The lower head of the cylinder 52 is likewise Vprovided with a port 65affording communication between-the cylinder 52 and the distributingpassage 6|. Said port 65 has a downwardly facing seat which is closed bya ball valve 56, urged against its seat by a suitably mounted spring 61.Said valve is adapted to 'be moved away from its seat near the extremityof the down stroke of the plunger 53, by an axial extension 69 of saidplunger 53. The cylinder 52 is further provided near its bottom portionwith a lateral port 1| which communicates with one end oi a passage 12.Said passage 12 communicates at its other end with the space in the feedcylinder 35 above its piston 38.

An enclosed cylinder providing therein a compression chamber 15 ismounted in any convenient position. The lower end portion of saidchamber 15 is connected with the distributing passage 6| by means of apipe 6|. Also extending outwardly ofthe lower end portion of thecylinder 15 is an exhaust or discharge pipe |55. Within the chamber 15is a piston I5I having an upwardly extending piston rod |52 projectinthrough the upper end of the cylinder 15 and suitably guided therein.The upper outer end of the piston rod |52 carries an indicator |53adapted to move over the face of a graduated feed pressure indicatingchart |54. The portion of the piston rod |52 within the chamber 15 issurrounded by a suitably tensioned coil spring |55. Said coiled springengages a piston at one end and the upper head of the cylinder 15 at theother end, so that when the piston is raised by virtue of the iluidintroduced thereinto from the pipe 6I the spring |55 will be compressedand the indicator |53 will move relative to delineations on the chart|54.

A relief passage 80 communicates at its lower end with the distributingpassage 6I. 'Ihe other end of said relief passage opens into the spaceof the cylinder 35 above the piston 38. Adjacent the junction of thepassage 80 with the passage 5| is a three-way valve 82 of anyconventional form, the valve being constructed and arranged so that inone adjustment it affords communication of the distributing passage 5iwith the relief passage 80 and also with the outlet branch 83 of saidvalve. In this adjustment the valve permits fluid to escape from theclosed passage 5| and also from the upper end of the cylinder 35. Inanother position of the valve both the cylinder 35 and the distributingpassage 5| are shutY oif from the outlet branch 83 and also from eachother.

The cylinder 35 is provided at its lower end with an interior upstandingshell 85 which is formed at its upper end with a release port and isprovided interiorly with a downwardly facing seat controlled by a ballvalve 81 normally held in its seat by a spring 88. Said shell 85 is incommunication with the distributing passage 6I by means of a branch 85.

The piston 38 is provided with a central or axial downwardly openingrecess 95 which closely receives the upper end of said shell when thepiston is near the lower limit of its travel. The piston is provided atthe top of its chambered portion with a central depending pin 8|, which,as the piston approaches the lower limit of its travel, extends throughthe port of the shell 85 and engages and unseats the valve 81 so as toprovide suitable communication between the distributing passage 6I and asmall area within the cylinder below the top of the recess 95. Atcertain times when it is not desired to so establish communicationbetween the distributing passage 6| and the interior of the shell 85,the branch 85 may be closed by any suitable form of cut-off valve 93located in the branch between the valve 81 and the distributing lpassageEl.

The lower head of the cylinder 35 is provided with a release port 35which opens into the space surrounding said cylinder. Preferably and asherein shown, the entire mechanism described, with the exception of thecylinder l5, and pipe 6I', is enclosed in a casing or shell lili! whichdepends from the table if! and may be attached thereto in any suitablemanner. Said shell constitutesa reservoir for a non-compressible fluidsuch as oil, which serves as a medium for trans- .mitting pressure tothe saw feeding mechanism and also as means for lubricating the severalmovable parts of the mechanism. Furthermore, as herein shown, certain ofthe cylinders and the various passages connecting them, may be formed ina single casting or unit.

The cylinder and plunger 5l constitute a pump for maintaining a suitablepressure in the system, while the cylinder' 52 and plunger 53 constitutemeans for intermittently diverting or transmitting small quantities ofthe fluid under pressure in said system through the passage l2 to thecylinder space in the feed chamber 35 above the piston 38 thereof` Sofar as the essential operation of the invention is concerned, the pumpcomprising the cylinder 53 and the plunger 5l, may be of any other form,as for instance, it may be a rotary pump and may or may not be connectedto the measuring pump to operate in synchrony therewith, the function ofthe pressure vpump being merely to maintain the proper pressure in thesystem, as herein shown.

However', the plungers 5l and 53 of the pressure and measuring pumpsrespectively, are shown as simultaneously operated from a single pointof power. To this end, a coupling yoke l [lil is loosely attached to theupper ends of said plungers 5l and 53 and the upper end of said yoke isconnected by a pin E05 with one arm of a bell crank lever 65. The bellcrank lever is pivotally mounted at |01 in a bearing on the table il).The other arm of said bell crank lever carries a roller E53 adapted toride on the periphery of a cam E35 which is fixed to the main driveshaft l5. Said roller VHet of the bell crank lever may be held inengagement with the periphery of said cam by means of a spiralcontractile spring M5 fixed at one end to the upstanding arm of saidbell crank lever and secured at its other end to a suitable stationarysupport. When thehigher portion o of said cam engages said roller theplungers 5! and 53 are depressed through the action of the bell cranklever and when the lower portion b of the cam engages the roller E58the` spring lill may serve to raise said plungers.

From the foregoing description it will be obvious that the operation ofthe feed mechanism described thus far is as follows: The plunger 54 isadapted to be depressed and raised once during each rotation of thedrive shaft and the cam I 39, and likewise the plunger 53 isfdepressedand raised in synchrony therewith. The relationship of the strokes ofthe pump plunger to the meas'- uring plunger is not essential to theoperation of the pump plunger. The operation of the measuring plunger tocause it to fall and rise once during each rotation of the cam H09 isessential, however, as the mechanism is so arranged to provide forproper timing of the feed mechanism.

The upward reciprocation of the plunger 5l serves to draw fluid from thetank or chamber IDD through the valved inlet 54 into the lower end ofthe cylinder 50. The depression of the the valve 66.

plunger 5| expels said fluid downwardly through the valved port Sil intothe distributing passage Y 6I. At the beginning of the operation of thesaw, the pressure space 6l is filled with nuid under normal pressure,and pressure is maintained in said passage and subsequently built upagainst the yielding force of the piston H53 which may be yieldinglyraised in the cylinder i5 against the predetermined tension of thespring E55. Upon setting the mechanism into operation the saw frame l5is, of course, reciprocated and the pump plunger 5l immediately beginsthe build up of pressure. Consequently the saw blade is initiallypressed lightly on the ivo-rk and the operation of sawing begins. Thefeed pressure is built up gradually against the piston 33 until yapredetermined feed pressure is attained. The control of this latterfeature is important in the present invention and will be hereinafterdescribed in detail. The feed pressure fo-rce is transferred against thepiston 38 by the action of the plunger 53 in its reciprocation bytrans-- ferring the liquid in the cylinder 52 below the plunger 53 whichtheretofore in the last stroke of the plunger 53 was withdrawn from thefeed cylinder by the ascent of said plunger and afterward, by thecontact of the pin 65 with the valve 56 whereby the valve is unseated todivert fluid under pressure from the pressure passage 5i to the feedcylinder 35. above its piston 33. valve 65 is opened at about the timethe saw has reached the beginning Yof its cutting stroke and thepressure of the fluid transmitted from the system into the cylinder 35acts to force the feed piston 38 downwardly and, through the piston rod39, link 5, and arm 43, to feed the saw to the work. The cylinder l5'contains the compressible vcoiled spring E55. As the fluid such as oilforced from the passage Gl through the pipe 5i into the lower portion ofthe cylinder 'i5 below the piston ki5l, the piston ii is graduallyraised, with the increase in pressure in the oil inthe system, and theraising of the piston i5i compresses the spring |55. The extent of thecompression of the spring determines the pressure at which the fluid isdelivered against the feed piston 38. The feed pressure on the piston 38is'maintained throughout the cutting stroke of the saw blade, which, inthe present instance, is the back stroke thereof. It will be understoodthat the fluid under pressure is transmitted to the feed cylinder 35abovethe piston 38 at a time when the bell crank roller H18 is travelingon the high Vportion of the cam IDS and at which time also theprojection 59 is thereby depressed to unseat However, the lower end ofthe plunger does not at this time pass the receiving end of the'port Hwhich communicates with the feed cylinder passage or by-pass l2.

At the end of the cutting stroke of the saw the bearing roller H38 ofthe bell crank lever |06 passes onto the lower portion b of the cam andthe spring H0 raises said plunger. Thus raised, a small portion of thefluidis withdrawn from the upper end of the feed cylinder 35 through theby-pass 12 to permit the piston 33 to slightly riseV and thereby permitthe saw blade to be raised sufficiently to vclear it from the bottom ofthe saw cut so that the saw will not ride on the bottom of the saw outin the return or non-cutting stroke of the saw. The valve 55 is closedby the pressure below, the moment the plunger'begins to rise. At thebeginning of each cutting stroke, after the saw is 75 set in operationto cut into a piece of work, the depression of the plunger 53 in thecylinder 52 will force the fluid contained in the cylinder below thepiston through the passage 12 into the feed cylinder before the valve 6Bis unseated by the plunger projection 59, so'that the first feedpressure exerted on the piston 38 at the beginning of each cuttingstroke of the saw is that due to the displacement of the fluid in thecylinder 52. This feed pressure is then supplemented by the higherpressure in the distributing passage 6I when the plunger descendssuiciently to unseat the valve 66.

The compressible spring |55 in the cylinder 15 serves as a cushioningmedium to cushion the feeding eifect of the fluid transmitted underpressure to the upper end of the feed cylinder. Should work ofunexpected hardness be encountered by the saw or should the cutting edgeof the saw be irregular, there will be some yielding of the saw feed dueto the cushioning eifect of the spring |55.

The provision of the central stud 9| in the recessed portion of thepiston 38, so located as to unseat the valve 81 which controls the portof the upstanding shell in the lower end of the feed cylinder, providesmeans to reduce the feed pressure on the saw blade as said saw blade isnearing the end of its cutting in the work when cutting round orirregular angled stock. It is desirable to thus reduce the feed pressurewhen cutting round stock for the reason that as the saw blade approachesthe lower arc of the stock the length of the saw cut decreases, and ifthe full operative pressure be maintained on the saw, there would be atendency to break the teeth of the saw blade, and also there would be atendency for the blade to break through the work in the final strokes ina manner to leave an objectionable bur on the stock. The reduction ofthe feed pressure on the saw when approaching the end of the cut is dueto the fact that the unseating of the valvev 81 by the stud 9| permitsfluid from the distributing space 6| to be by-passed to the under sideof the feed piston above the shell B5, and the pressure from thedistributing passage 6| acts on the Vlower portion of the lower pistonface, representing the upper wall of the recess, to effect adifferential pressure from the same source against unequal areas of theupper and lower faces of the piston. This has the effect to neutralize aportion of the feed pressure acting on the upper face of the piston andto reduce the feed pressure.

When operating on work providing uniform support for the saw teeth,throughout the cut,l

such as flat bars and the like, such differential feed pressure will notbe required. In this event, therefore, the valve 93 may be closed sothat contact of the stud 9! with the valve 31 does Vnot by-pass anyportion of the pressure fluid to act on the lower face of the feedpiston 38.

In conjunction with the feed pressure regulating and cushioning cylinder15 there is provided an instrumentality for selectively regulating themaximum amount of the build-up of pressure attainable. It is obviousthat the lower end portion of the cylinder 15 must be provided with anoil discharge port and the pipe 55 previously |58 which may lead to anyconvenient interior portion of the tank |00. It is intended that the`amount of opening movement of the valve |51 and consequent by-passingor discharge of oil through the pipe |58 be commensurate with the amountof pressure build-up within the fluid system. For this purpose,therefore, the valve |51 may be formed with an elongated valve rod |59extending through and axially of the fitting IE5. On a portion of thevalve rod |59 considerably removed from the valve |51 there is slidablymounted a disc |60 against the face of which one end of a coiled springIGI rests. The other end of the coiled spring engages an outer face ofthe valve |51.

A side wall portion of the fitting |55 is formed with an elongated slot|62 through which a pin |63, carried by the disc 60, projects. 'I'hespring ISI is of a predetermined tension and it is intended that thesame be maintained, for a certain piece of work, in a predeterminedposition of elongation, thereby governing the amount of fluid pressurerequired against the other side of the Valve |51, to cause opening ofsaid valve. Therefore, there is mounted on a suitable support, adjacentthe fitting E55, a bracket |54 formed with an upper face portion havinggraduations and numerical designations delineated thereon in an arc.'Ihe graduations may be of any selected value and as illustrated runfrom 1 to '1. As will app-ear hereinafter these graduations correspondwith similar graduations appearing on a portion of the chart |54 andrepresent selectible settings for the attainment of predeterminedmaximum pressure build-ups. It is evident from an inspection of thechart |54 that opposite the vertical row of numbers ranging from l to 7there is another vertical row ranging from to 250. Said latter numbersindicate pounds of pressure applied to the tool and it ywill be seenthat number 4 for instance indicates or corresponds with a build-upfluid pressure of pounds. As will appear, if the numeral 4 is selectedon the face of the bracket |64 and the device is set accordingly, themaxi- 'mum build-up pressure attainable is 175 pounds ,and the indicator|53, during the operation of the machine, will slowly rise until itreaches the n umeral 4 on the chart |54 whereupon it will rise no higherand the pressure will build up no higher because fluid pressure in thepipe I 5l) will have overcome the resistance of the spring I6| andcaused a full opening of the valve I 51 to by-pass fluid.

To maintain the disc |60 in a predetermined position with the consequentdesired elongation of the spring I6| there is pivotally mounted on thebracket |64, intermediate its ends, a turnable indicator hand IE5. Thelower end of the hand |65 is adapted to engage in all positions againstthe extended pin |53. The hand |65 may be set in a desired position byany suitable means as by engaging a movable pin element IGS-with any ofa series of depressions I 51 in the face of the bracket |54. Obviouslyif the hand |65 is swung relatively far in a clockwise direction withrespect to Fig. 2 its lower end will move the disc |50 inwardly on therod |59, compressing the spring ISI. In this event it will mean that ahigh built-up pressure must be attained before the resistance of thespring is overcome to cau-se opening of the valve |51 to by-pass fluid.Conversely if the hand |65 is in a reverse position its other end willbe further to the right in Fig. 2

Vso

permitting'an outward'movement of the disc |60 with a consequentelongation of the spring |6|,. Under this condition less built-uppressure will be required to cause an opening of the by-pass valve |57.

It will therefore be seen that as pressure is built up in the system thepiston |5| is raised and the indicator |53 indicates on the chart |515the amount of pressure attained at any particular time. Also, by virtueof the fitting |55 and associated parts, any setting of the hand |5 willso control the opening movements of the by-pass valve |51 that saidby-pass valve will fully open upon the indicator |53 reaching a numberon the chart |56 corresponding with the setting of the hand |65.

It will thus be understood that there is provided a feed mechanism whichfeeds the saw blade to the stock with a delicate pressure at thebeginning of the operation and gradually builds up the pressure to apredetermined point as the Work proceeds, and which is also constructedto reduce the feed pressure as the saw blade approaches the end of thecut. The regulation of the feed pressure at the beginning and at the endof the cut is advantageous inasmuch as it avoids undue pressure oncertain teeth of the saw blade and also avoids burs on the stock at theend of the cut. Moreover the light pressure at the beginning of the cutmakes it easier to direct the saw blade to the proper point on thestock, and alsov saves wear on the teeth of the saw blade at thebeginning of the cut, and the advantage of so applying the saw blade tothe 'Work with a light pressure at the beginning of the cut is that timeis given for the cutting compound to begin to flow freely on .the bladeand the v/ork before substantial feed pressure is exerted on theV saw.In the present construction, although the saw begins to cut immediatelyupon operation of the machine, when the saw blade is in contact with thework, substantial feed pres'- sure of the saw blade on the work is notexerted e until sufficient time has passed for a suitable amount ofcutting compound to have Areached the blade and stock.

At the end of the saw cut on any given piece of stock being operatedupon, and preparatory to allowing the saw frame to rise freely underVthe influence of the over-balancing spring 22, it is necessary thatiluid under pressure be released from the feed cylinder above the piston38. It is also necessary that the fluid under pressure be released fromthe distributing space 6| so that in the beginning of the next cuttingoperation the feed pressure during the first cutting strokes will belight and will be gradually built up to normal operating pressure as thework proceeds. This is effected by adjusting the three- Way valve 82 soas to connect the drain pipe 80 and the distributing passage 6| to theoutlet branch 83 of said three-way valve. The means for accomplishingthis movement of the valve is not shown but obviously it may beaccomplished either manually or by some automatic means associated witha part of the machine.

In practice, the avoiding of the building up of saw, the feed mechanismmay be applied to `other cutting tools Where the-conditions obtain offeeding the tool to its work .and retracting it there- From theforegoing. description it will be 'obvious that the improved mechanismsupplies means for feeding .the tool to the work with graduallyincreasing pressure and for cushioning the return strokes. The improvedpressure build-up and cushioning cylinder 15 is very important in thesuccessful functioning of the machine as it permits immediate operationof the saw, with the subsequent gradual build-up of pressure to apredetermined amount. The amount of pressure to be eventually attainedis, of course, regulatable and the hand |65 movable over the indicatingface of the bracket |64 provides simple means for making the desiredsetting which will correspond with the ultimate position attained by theindicator |53 with respect tothe chart |54. vThe mechanism is relativelysimpleand extremely efficient in operation, and is Well adapted for thepurposes described.

I claim as my invention: Y

1. Feed means for power hack saw machines comprising, in combination, amovable saw supporting guide, a feed cylinder, a piston thereinoperatively connected to said guide, a closed distributing space tocontain fluid, means to Vforce fluid under'pressure to said space, meansoperative during each cutting stroke of the saw to divert a quantity ofsaid fluid to the feed cylinder against the piston torfeed the saw tothe work, means operative during each non-cutting stroke of the saw torelease a quantity of Yfluid from said cylinder, a pressure chamber incommunica- `tion with the distributing space, a member normally exposedto said chamber and constantly movable by variations of pressuretherein, and resilient -means coacting Vwith said member to predeterminethe maximum attainable pressure in said chamber while preventing releaseof pressure therein.

2. Feed means for power hack saw machines comprising, in combination, amovable saw supporting guide, a feed cylinder, a piston thereinoperatively connected to saidguide, a closed distributing space tocontain fluid, means to force fluid under pressure to said space, meansoperative during each cutting stroke of the saw to divert a quantity ofsaid fluid to the feed cylinder against the piston to feed the saw tothe Work, means operative during each non-cutting stroke of the saw torelease a quantity of fluid from said cylinder, a member normallyexposed to ksaid chamber and constantly movable by variations ofpressure therein, resilient means coacting with said chamber topredetermine the maximum attainable pressure in said chamber whilepreventing release of pressure therein, and means to regulably releasepressure from said space.

3. Feed means for power hack saw machines comprising, in combination, amovable saw supporting guide, a feed cylinder, a'piston thereinoperatively connected to said guide, a closed dis# tributing space tocontain fiuid, means to supply fluid under pressure to `saiddistributing space, a measuring cylinder provided with a valved portcommunicating with said distributing space and provided with a passagewhich connects it to the feed cylinder above said piston, a plunger inthe measuring cylinder, means to connect said plunger to the sawoperating mechanism to cause it to reciprocate duringeach operation ofthe saw, m-eans carried by the plunger for opening the valved portduring the cutting stroke of the saw, a variable pressure chamber incommunication with the distributing space, a member normally exposed tosaid chamber and constantly movable by variations of pressure therein,and resilient means coacting with said member to predetermine themaximum attainable pressure in said chamber while preventing release ofthe pressure therein.

4. Feed means for power hack saw machines comprising, in combination, amovable saw supporting guide which is overbalanced to move the supportaway from the work table during the noncutting stroke of the saw,hydraulic feed means to feed the saw to the work including a closeddistributing space to contain fluid, means for building up fluidpressure in said space, a pressure chamber in communication with saiddistributing space, a piston in said chamber and movable against theforce of a confined spring, said piston having a piston rod extendingexteriorly of said chamber, a pressure indicating chart, and anindicator carried by the outer end of said piston rod and movableadjacentY said chart to indicate attained fluid pressures.

5. Feed means for power hack saw machines comprising, in combination, amovable saw supporting guide which is o-verbalanced to move the supportaway from the work table during the non-cutting stroke of the saw,hydraulic feed means to feed the saw to the work including a closeddistributing space to contain fluid, means for building up fluidpressure in said space, a pressure chamber in communication with saiddistributing space, a piston in said chamber and movable against theforce of a confined spring, said piston having a piston rodV extendingexteriorly of said chamber, a pressure indicating chart, an indicatorcarried by the outer end of said piston rod and movable adjacent saidchart to indicate attained fluid pressure, a fluid by` pass pipeextending outwardly of said chamber, a valve in said pipe adapted to beopened by predetermined fluid pressure thereagainst, and meansregulating the freedom of movement 0f said valve, said means controllingthe amount of pressure required to open said valve.

6. A power hack saw machine comprising, in combination, a saw supportingguide movable to# ward and from the work, and hydraulic feed meansoperatively connected to said guide to exert pressure thereon to feedthe saw to its work during the cutting stroke thereof, said feed meansbeing formed to immediately lightly apply the saw to the work during thefirst few cutting strokes and having a manually manipulable feedpressure control for pre-setting the maximum attainable feed pressure soas to gradually, yieldingly increase the feed pressure to a definite andpredetermined value as the cutting proceeds and during subsequentcutting strokes, the feed pressure during said subsequent cuttingstrokes being in excess of that during the initial cutting strokes.

'7. In a power hack saw, a movable saw supporting guide, meansoperatively connected to said guide to feed the saw to its work duringthe cutting stroke, means connected with said feed means for initiallylightly applying the saw to the work during all portions of the iirstfew cutting strokes and gradually, yieldingly increasing the feedpressure during all portions of subsequent cutting strokes to apredetermined point as the cutting proceeds, said means operatingdirectly on said fee-d means and including a spring, there being meansfor automatically compressing the spring at a controllable rate duringcutting operations.

8. A power hack saw machine comprising in combination, a saw supportingguide movable to- Ward and from the work, and hydraulic feed meansoperatively connected to said guide to feed the saw to its work duringthe cutting stroke thereof, said feed means being constructed with.hydraulically controlled means to immediately lightly apply the saw tothe work during the first few cutting strokes and also having adjustablespring controlled means affecting said hydraulic means for gradually,continuously, and yieldingly increasing the feed pressure duringsubsequent Y cutting strokes to a predetermined point, whereby the feedpressure during any portion of said subsequent cutting strokes is inexcess of that during the initial cutting strokes.

. ANDREW RASMUSSEN.

